Light-emitting device, electronic device, and lighting device

ABSTRACT

A lightweight flexible light-emitting device that is less likely to be broken is provided. The light-emitting device includes a first flexible substrate, a second flexible substrate, an element layer, a first bonding layer, and a second bonding layer. The element layer includes a light-emitting element. The element layer is provided between the first flexible substrate and the second flexible substrate. The first bonding layer is provided between the first flexible substrate and the element layer. The second bonding layer is provided between the second flexible substrate and the element layer. The first and second bonding layers are in contact with each other on the outer side of an end portion of the element layer. The first and second flexible substrates are in contact with each other on the outer side of the end portions of the element layer, the first bonding layer, and the second bonding layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an object, a method, and amanufacturing method. In addition, the present invention relates to aprocess, a machine, manufacture, and a composition of matter. Oneembodiment of the present invention particularly relates to asemiconductor device, a light-emitting device, a display device, anelectronic device, a lighting device, and a manufacturing methodthereof. One embodiment of the present invention particularly relates toa light-emitting device, a display device, an electronic device, and alighting device utilizing electroluminescence (hereinafter also referredto as EL) and a manufacturing method thereof.

2. Description of the Related Art

Recent light-emitting devices and display devices are expected to beapplied to a variety of uses and become diversified.

For example, light-emitting devices and display devices for mobiledevices and the like are required to be thin, lightweight, and lesslikely to be broken.

Light-emitting elements utilizing EL (also referred to as EL elements)have features such as ease of thinning and lightening, high-speedresponse to input signal, and driving with a direct-current low voltagesource; therefore, application of the light-emitting elements tolight-emitting devices and display devices has been proposed.

For example, Patent Document 1 discloses a flexible active matrixlight-emitting device in which an organic EL element and a transistorserving as a switching element are provided over a film substrate.

PATENT DOCUMENT

-   [Patent Document 1] Japanese Published Patent Application No.    2003-174153

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide anovel light-emitting device, display device, electronic device, orlighting device. Another object of one embodiment of the presentinvention is to provide a lightweight light-emitting device, displaydevice, electronic device, or lighting device. Another object of oneembodiment of the present invention is to provide a highly reliablelight-emitting device, display device, electronic device, or lightingdevice. Another object of one embodiment of the present invention is toprovide a light-emitting device, display device, electronic device, orlighting device that is less likely to be broken. Another object of oneembodiment of the present invention is to provide a thin light-emittingdevice, display device, electronic device, or lighting device. Anotherobject of one embodiment of the present invention is to provide alight-emitting device, display device, electronic device, or lightingdevice with high light extraction efficiency. Another object of oneembodiment of the present invention is to provide a light-emittingdevice, display device, electronic device, or lighting device with highluminance. Another object of one embodiment of the present invention isto provide a light-emitting device, display device, electronic device,or lighting device with low power consumption.

Another object of one embodiment of the present invention is to providea lightweight flexible light-emitting device, display device, electronicdevice, or lighting device that is less likely to be broken.

Note that in one embodiment of the present invention, there is no needto achieve all the objects.

A light-emitting device of one embodiment of the present inventionincludes a first flexible substrate, a second flexible substrate, anelement layer, a first bonding layer, and a second bonding layer. Theelement layer includes a light-emitting element. The element layer isprovided between the first flexible substrate and the second flexiblesubstrate. The first bonding layer is provided between the firstflexible substrate and the element layer. The second bonding layer isprovided between the second flexible substrate and the element layer.The first bonding layer and the second bonding layer are in contact witheach other on the outer side of an end portion of the element layer. Thefirst flexible substrate and the second flexible substrate overlap witheach other on the outer side of end portions of the element layer, thefirst bonding layer, and the second bonding layer. In one embodiment ofthe present invention, the first flexible substrate and the secondflexible substrate may be in contact with each other.

Another embodiment of the present invention is a light-emitting devicewhich includes a first flexible substrate, a second flexible substrate,an element layer, a first bonding layer, a second bonding layer, and athird bonding layer. The element layer includes a light-emittingelement. The element layer is provided between the first flexiblesubstrate and the second flexible substrate. The first bonding layer isprovided between the first flexible substrate and the element layer. Thesecond bonding layer is provided between the second flexible substrateand the element layer. The third bonding layer, the first flexiblesubstrate, and the second flexible substrate overlap with one another onthe outer side of end portions of the element layer, the first bondinglayer, and the second bonding layer.

For example, it is preferable that the first flexible substrate and thesecond flexible substrate be attached to each other with alow-melting-point glass, a thermoplastic resin, or the liketherebetween. In other words, it is preferable that the third bondinglayer contain a low-melting-point glass or a thermoplastic resin.

Another embodiment of the present invention is a light-emitting devicewhich includes a first flexible substrate, a second flexible substrate,an element layer, a first bonding layer, and a second bonding layer. Theelement layer includes a light-emitting element. The element layer isprovided between the first flexible substrate and the second flexiblesubstrate. The first bonding layer is provided between the firstflexible substrate and the element layer. The second bonding layer isprovided between the second flexible substrate and the element layer.The second bonding layer, the first flexible substrate, and the secondflexible substrate overlap with one another on the outer side of endportions of the element layer and the first bonding layer. Furthermore,the first flexible substrate and the second flexible substrate may be incontact with each other on the outer side of end portions of the elementlayer, the first bonding layer, and the second bonding layer.

In the light-emitting device of each of the above embodiments, it ispreferable that the absolute value of a difference between the thermalexpansion coefficient of the first flexible substrate and the thermalexpansion coefficient of the second flexible substrate be smaller thanor equal to 10% of the thermal expansion coefficient of the firstflexible substrate or the thermal expansion coefficient of the secondflexible substrate.

In the light-emitting device of each of the above embodiments, it ispreferable that the first flexible substrate and the second flexiblesubstrate contain the same material.

An electronic device or a lighting device including the light-emittingdevice of each of the above embodiments is also one embodiment of thepresent invention.

Note that the light-emitting device in this specification includes, inits category, a display device using a light-emitting element. Further,the category of the light-emitting device in this specification includesa module in which a light-emitting element is provided with a connectorsuch as an anisotropic conductive film or a TCP (tape carrier package);a module having a TCP at the end of which a printed wiring board isprovided; and a module in which an IC (integrated circuit) is directlymounted on a light-emitting element by a COG (chip on glass) method.Furthermore, the category includes a light-emitting device which is usedin lighting equipment or the like.

In one embodiment of the present invention, a novel light-emittingdevice, display device, electronic device, or lighting device can beprovided. In one embodiment of the present invention, a lightweightlight-emitting device, display device, electronic device, or lightingdevice can be provided. In one embodiment of the present invention, ahighly reliable light-emitting device, display device, electronicdevice, or lighting device can be provided. In one embodiment of thepresent invention, a light-emitting device, display device, electronicdevice, or lighting device that is less likely to be broken can beprovided. In one embodiment of the present invention, a thinlight-emitting device, display device, electronic device, or lightingdevice can be provided. In one embodiment of the present invention, alight-emitting device, display device, electronic device, or lightingdevice with high light extraction efficiency can be provided. In oneembodiment of the present invention, a light-emitting device, displaydevice, electronic device, or lighting device with high luminance can beprovided. In one embodiment of the present invention, a light-emittingdevice, display device, electronic device, or lighting device with lowpower consumption can be provided.

In one embodiment of the present invention, a lightweight flexiblelight-emitting device, display device, electronic device, or lightingdevice that is less likely to be broken can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C illustrate light-emitting devices.

FIGS. 2A to 2G illustrate light-emitting devices.

FIGS. 3A and 3B each illustrate a light-emitting device.

FIGS. 4A and 4B each illustrate a light-emitting device.

FIGS. 5A to 5C each illustrate a light-emitting device.

FIGS. 6A to 6C illustrate a method for manufacturing a light-emittingdevice.

FIGS. 7A to 7C illustrate a method for manufacturing a light-emittingdevice.

FIGS. 8A to 8C illustrate an electronic device.

FIG. 9 illustrates an electronic device.

FIGS. 10A to 10E illustrate electronic devices.

FIGS. 11A to 11C illustrate an electronic device.

FIGS. 12A to 12G illustrate electronic devices.

FIGS. 13A and 13B each illustrate a light-emitting device.

FIGS. 14A and 14B each illustrate a light-emitting device.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to the drawings.Note that the present invention is not limited to the followingdescription, and it will be easily understood by those skilled in theart that various changes and modifications can be made without departingfrom the spirit and scope of the present invention. Therefore, thepresent invention should not be construed as being limited to thedescription in the following embodiments.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Further, the same hatch pattern is applied tosimilar functions, and these are not especially denoted by referencenumerals in some cases.

In addition, the position, size, range, or the like of each structureillustrated in drawings and the like is not accurately represented insome cases for easy understanding. Therefore, the disclosed invention isnot necessarily limited to the position, size, range, or the likedisclosed in the drawings and the like.

Embodiment 1

In this embodiment, a light-emitting device of one embodiment of thepresent invention will be described with reference to FIGS. 1A to 1C,FIGS. 2A to 2G, FIGS. 3A and 3B, FIGS. 4A and 4B, FIGS. 5A to 5C, FIGS.6A to 6C, FIGS. 7A to 7C, FIGS. 13A and 13B, and FIGS. 14A and 14B.

A structure of the light-emitting device of one embodiment of thepresent invention will be described.

FIG. 1A illustrates a plan view of the light-emitting device of oneembodiment of the present invention, and FIG. 1B illustrates across-sectional view of the light-emitting device of one embodiment ofthe present invention. The light-emitting device includes a lightextraction portion 104 and a driver circuit portion 106.

In the light-emitting device illustrated in FIG. 1B, a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103 are sequentially stacked. Theelement layer 101 includes a light-emitting element. A conductive layerincluded in the element layer 101 and an FPC 108 are electricallyconnected to each other by a connector 215.

FIG. 2A illustrates a plan view of a light-emitting device of anotherembodiment of the present invention, and FIGS. 2B to 2G each illustratea cross-sectional view of the light-emitting device of the otherembodiment of the present invention. The light-emitting device includesa light extraction portion 104 and a driver circuit portion 106.

In the light-emitting device illustrated in FIG. 2B, a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103 are sequentially stacked. Theelement layer 101 includes a light-emitting element. A conductive layerincluded in the element layer 101 and an FPC 108 are electricallyconnected to each other by a connector 215.

An organic compound or a metal material used in the light-emittingelement easily reacts with an impurity such as moisture or oxygen. Thereaction of the organic compound or the metal material with the impurityresults in a significant decrease in lifetime of the light-emittingelement. In one embodiment of the present invention, the bonding layer105 and the bonding layer 203 are in contact with each other on theouter side of an end portion of the element layer 101. Such a structurecan suppress the entry of an impurity such as atmospheric moisture intothe element layer 101. Accordingly, a decrease in reliability of thelight-emitting device can be suppressed, which is preferable.

In the light-emitting device illustrated in FIG. 2C, a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103 are sequentially stacked. Aconductive layer included in the element layer 101 and an FPC 108 areelectrically connected to each other by a connector 215. The flexiblesubstrate 201 and the flexible substrate 103 are in contact with eachother on the outer side of an end portion of the element layer 101.

In order to increase the adhesion between the flexible substrate 201 andthe flexible substrate 103, it is preferable that an adhesive, a glassfrit (low-melting-point glass), a thermoplastic resin, or the like beplaced in contact with the flexible substrate 201 and the flexiblesubstrate 103 and be cured or welded. FIG. 2E illustrates an example inwhich the flexible substrate 201 and the flexible substrate 103 areattached 15 to each other with a bonding layer 206 provided on the outerside of an end portion of the element layer. For the bonding layer 206,an adhesive, a glass frit (low-melting-point glass), a thermoplasticresin, or the like can be used. Alternatively, the flexible substrate201 and the flexible substrate 103 may be welded directly. The flexiblesubstrate used in one embodiment of the present invention has a lowthermal expansion coefficient and a high heat resistance: therefore, thelight-emitting device is not easily damaged even by local heating suchas thermocompression bonding. Such a structure is preferable because animpurity such as atmospheric moisture does not easily enter the elementlayer 101 and a decrease in reliability of the light-emitting device canbe suppressed.

In the light-emitting device illustrated in FIG. 2D, a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103 are sequentially stacked. Aconductive layer included in the element layer 101 and an FPC 108 areelectrically connected to each other by a connector 215. The bondinglayer 105 and the bonding layer 203 are in contact with each other onthe outer side of an end portion of the element layer 101. The flexiblesubstrate 201 and the flexible substrate 103 are in contact with eachother on the outer side of end portions of the element layer 101, thebonding layer 203, and the bonding layer 105. As described for thelight-emitting device illustrated in FIG. 2E, in order to increase theadhesion between the flexible substrate 201 and the flexible substrate103, it is preferable that an adhesive, a glass frit (low-melting-pointglass), a thermoplastic resin, or the like be placed in contact with theflexible substrate 201 and the flexible substrate 103 and be cured orwelded. In other words, in addition to the structure in FIG. 2D, abonding layer 206 may be provided on the outer side of the end portionof the element layer. Alternatively, the flexible substrate 201 and theflexible substrate 103 may be welded directly.

As in a light-emitting device illustrated in FIG. 2F, a bonding layer105, a flexible substrate 201, and a flexible substrate 103 may overlapwith one another on the outer side of end portions of an element layer101 and a bonding layer 203. The bonding layer 105 covers the endportions of the element layer 101 and the bonding layer 203. Theflexible substrate 201 and the flexible substrate 103 are attached toeach other with the bonding layer 105 therebetween. Further, asillustrated in FIG. 2G, the flexible substrate 201 and the flexiblesubstrate 103 may be in contact with each other on the outer side of endportions of the element layer 101, the bonding layer 203, and thebonding layer 105.

In the case where the flexible substrate 201 and the flexible substrate103 are in contact with each other on the outer side of the end portionof the element layer 101 as illustrated in FIG. 2C, 2D, or 2G, theadhesion can be increased by using materials having similar properties.Therefore, it is preferable to use the same material for a pair offlexible substrates.

For the flexible substrates, a material such as glass, quartz, ceramics,sapphire, or an organic resin can be used.

Examples of glass include alkali-free glass, barium borosilicate glass,aluminoborosilicate glass, and the like.

Examples of a material having flexibility and a light-transmittingproperty with respect to visible light include glass that is thin enoughto have flexibility, polyester resins such as polyethylene terephthalate(PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, apolyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC)resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefinresin, a polystyrene resin, a polyamide imide resin, and a polyvinylchloride resin. In particular, a material whose thermal expansioncoefficient is low is preferred, and for example, a polyamide imideresin, a polyimide resin, or PET can be suitably used. A substrate inwhich a glass fiber is impregnated with an organic resin or a substratewhose thermal expansion coefficient is reduced by mixing an organicresin with an inorganic filler can also be used.

Note that in the light-emitting device of one embodiment of the presentinvention, a substrate having a poor light-transmitting property, suchas a metal substrate, may be used as a flexible substrate which does notneed to transmit light. There is no particular limitation on a materialof the metal substrate, but it is preferable to use, for example,aluminum, copper, nickel, or a metal alloy such as an aluminum alloy orstainless steel.

In the light-emitting device of one embodiment of the present invention,it is preferable that the absolute value of a difference between thethermal expansion coefficients of the pair of flexible substrates besmaller than or equal to 10% of the thermal expansion coefficient of atleast one of the pair of flexible substrates. By decreasing thedifference between the thermal expansion coefficients of the pair offlexible substrates, the warpage of the light-emitting device to oneside can be suppressed. A difference in the degree of expansion andcontraction due to heat between the pair of flexible substrates is acause of generation of a crack in the light-emitting device. Also inthis regard, it is preferable to use the same material for the pair offlexible substrates. Accordingly, the difference between the thermalexpansion coefficients of the pair of flexible substrates can bedecreased.

Specific Example 1

FIG. 1A is a plan view of the light-emitting device of one embodiment ofthe present invention, and FIG. 1C is an example of a cross-sectionalview taken along dashed-dotted line A1-A2 in FIG. 1A.

The light-emitting device illustrated in FIG. 1C includes a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103. The element layer 101 includesan insulating layer 205, a plurality of transistors, a conductive layer157, an insulating layer 207, an insulating layer 209, a plurality oflight-emitting elements, an insulating layer 211, a bonding layer 213,an overcoat 261, a coloring layer 259, a light-blocking layer 257, andan insulating layer 255.

The conductive layer 157 is electrically connected to an FPC 108 via aconnector 215. Note that FIG. 1C illustrates an example in which the FPC108 overlaps with the flexible substrate 103; however, one embodiment ofthe present invention is not limited to this example. For example, inthe case where the flexible substrate 103 has a smaller area than thatof the flexible substrate 201 as illustrated in FIG. 13A, the FPC 108may be provided in a region where the flexible substrate 201 and theflexible substrate 103 do not overlap with each other (in other words,the flexible substrate 103 and the FPC 108 do not necessarily overlapwith each other).

A light-emitting element 230 includes a lower electrode 231, an EL layer233, and an upper electrode 235. The lower electrode 231 is electricallyconnected to a source electrode or a drain electrode of a transistor240. An end portion of the lower electrode 231 is covered with theinsulating layer 211. The light-emitting element 230 has a top emissionstructure. The upper electrode 235 has a light-transmitting property andtransmits light emitted from the EL layer 233.

The coloring layer 259 is provided to overlap with the light-emittingelement 230, and the light-blocking layer 257 is provided to overlapwith the insulating layer 211. The coloring layer 259 and thelight-blocking layer 257 are covered with the overcoat 261. The spacebetween the light-emitting element 230 and the overcoat 261 is filledwith the bonding layer 213.

Note that the light-emitting device of one embodiment of the presentinvention may include the light-emitting element 230 which does notoverlap with the coloring layer 259 as illustrated in FIG. 13B. Forexample, in the case where one pixel includes four sub-pixels which arered, blue, green, and white sub-pixels, the coloring layer 259 is notnecessarily provided in the white sub-pixel. Accordingly, the amount oflight absorbed by the coloring layer can be reduced, and thus, the powerconsumption of the light-emitting device can be reduced. With the use ofdifferent materials for an EL layer 233a and an EL layer 233b,light-emitting elements exhibiting different colors may be manufacturedin pixels.

The light-emitting device includes a plurality of transistors includingthe transistor 240 in a light extraction portion 104 and a drivercircuit portion 106. The transistor 240 is provided over the insulatinglayer 205. The insulating layer 205 and the flexible substrate 201 areattached to each other with the bonding layer 203. The insulating layer255 and the flexible substrate 103 are attached to each other with thebonding layer 105. It is preferable to use films with low waterpermeability for the insulating layer 205 and the insulating layer 255,in which case an impurity such as water can be prevented from enteringthe light-emitting element 230 or the transistor 240, leading toimproved reliability of the light-emitting device.

The light-emitting device in Specific Example 1 can be manufactured inthe following manner: the insulating layer 205, the transistor 240, andthe light-emitting element 230 are formed over a formation substratewith high heat resistance; the formation substrate is separated; and theinsulating layer 205, the transistor 240, and the light-emitting element230 are transferred to the flexible substrate 201 and attached theretowith the bonding layer 203. The light-emitting device in SpecificExample 1 can be manufactured in the following manner: the insulatinglayer 255, the coloring layer 259, and the light-blocking layer 257 areformed over a formation substrate with high heat resistance; theformation substrate is separated; and the insulating layer 255, thecoloring layer 259, and the light-blocking layer 257 are transferred tothe flexible substrate 103 and attached thereto with the bonding layer105.

In the case where a material with low heat resistance (e.g. resin) isused for a substrate, it is difficult to expose the substrate to hightemperature in the manufacturing process. Thus, there is a limitation onconditions for forming a transistor and an insulating film over thesubstrate. Further, in the case where a material with high waterpermeability (e.g., resin) is used for a substrate of a light-emittingdevice, it is preferable to expose the substrate to high temperature andform a film with low water permeability between the substrate and alight-emitting element. In the manufacturing method of this embodiment,a transistor and the like can be formed over a formation substratehaving high heat resistance; thus, the substrate can be exposed to hightemperature and a highly reliable transistor and an insulating film withsufficiently low water permeability can be formed. Then, the transistorand the insulating film are transferred to a substrate with low heatresistance, whereby a highly reliable light-emitting device can bemanufactured. Thus, with one embodiment of the present invention, a thinand/or lightweight light-emitting device with high reliability can beprovided. Details of the manufacturing method will be described later.

In Specific Example 1, light emitted from the light-emitting element 230is extracted through the flexible substrate 103. Therefore, a materialwhich transmits visible light is used for the flexible substrate 103. Itis preferable that the flexible substrate 103 have a visible-lighttransmittance higher than that of the bonding layer 105. In that case, adecrease in light extraction efficiency of the light-emitting device canbe suppressed.

It is also preferable that the absolute value of a difference in thermalexpansion coefficient between the flexible substrate 103 and theflexible substrate 201 be smaller than or equal to 10% of the thermalexpansion coefficient of the flexible substrate 103 or the flexiblesubstrate 201. In that case, it is possible to suppress warpage of thelight-emitting device, generation of a crack in the light-emittingdevice, or the like.

In the case where the flexible substrate 201 and the flexible substrate103 are in contact with each other on the outer side of the end portionof the element layer 101 as illustrated in FIG. 2C, 2D, or 2G, theadhesion can be increased by using materials having similar properties.This structure is preferable because an impurity such as atmosphericmoisture does not easily enter the element layer 101 and a decrease inreliability of the light-emitting device can be suppressed. Further, asillustrated in FIG. 2B, 2E, or 2F, the flexible substrate 201 and theflexible substrate 103 may be attached to each other with the bondinglayer 206, the bonding layer 105, or the like.

Specific Example 2

FIG. 3A illustrates another example of the light extraction portion 104in the light-emitting device. The light-emitting device illustrated inFIG. 3A is capable of touch operation. In the following specificexamples, description of components similar to those in Specific Example1 is omitted.

The light-emitting device illustrated in FIG. 3A includes a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103. The element layer 101 includesan insulating layer 205, a plurality of transistors, an insulating layer207, an insulating layer 209, a plurality of light-emitting elements, aninsulating layer 211, an insulating layer 217, a bonding layer 213, anovercoat 261, a coloring layer 259, a light-blocking layer 257, aplurality of light-receiving elements, a conductive layer 281, aconductive layer 283, an insulating layer 291, an insulating layer 293,an insulating layer 295, and an insulating layer 255.

Specific Example 2 includes the insulating layer 217 over the insulatinglayer 211. The space between the flexible substrate 103 and the flexiblesubstrate 201 can be adjusted with the insulating layer 217.

FIG. 3A illustrates an example in which a light-receiving element isprovided between the insulating layer 255 and the bonding layer 213.Since the light-receiving element can be placed to overlap with atransistor or a wiring, the light-emitting device can be provided with atouch sensor without a decrease in the aperture ratio of a pixel(light-emitting element).

As the light-receiving element included in the light-emitting device,for example, a PN photodiode or a PIN photodiode can be used. In thisembodiment, a PIN photodiode including a p-type semiconductor layer 271,an i-type semiconductor layer 273, and an n-type semiconductor layer 275is used as the light-receiving element.

Note that the i-type semiconductor layer 273 is a semiconductor in whichthe concentration of each of an impurity imparting p-type conductivityand an impurity imparting n-type conductivity is 1×10²⁰ cm⁻³ or less andwhich has photoconductivity 100 or more times as high as darkconductivity. The i-type semiconductor layer 273 also includes, in itscategory, a semiconductor that contains an impurity element belonging toGroup 13 or Group 15 of the periodic table. In other words, since ani-type semiconductor has weak n-type electric conductivity when animpurity element for controlling valence electrons is not addedintentionally, the i-type semiconductor layer 273 includes, in itscategory, a semiconductor to which an impurity element imparting p-typeconductivity is added intentionally or unintentionally at the time ofdeposition or after the deposition.

The light-blocking layer 257 is closer to the flexible substrate 201than is the light-receiving element and overlaps with thelight-receiving element. The light-blocking layer 257 between thelight-receiving element and the bonding layer 213 can prevent thelight-receiving element from being irradiated with light emitted fromthe light-emitting element 230.

The conductive layer 281 and the conductive layer 283 are electricallyconnected to the light-receiving element. The conductive layer 281preferably transmits light incident on the light-receiving element. Theconductive layer 283 preferably blocks light incident on thelight-receiving element.

It is preferable to provide an optical touch sensor between the flexiblesubstrate 103 and the bonding layer 213 because the optical touch sensoris less likely to be affected by light emitted from the light-emittingelement 230 and can have improved S/N ratio.

The flexible substrate 103 and the flexible substrate 201 are preferablythe same as those in Specific Example 1.

Specific Example 3

FIG. 3B illustrates another example of the light extraction portion 104in the light-emitting device. The light-emitting device illustrated inFIG. 3B is capable of touch operation.

The light-emitting device illustrated in FIG. 3B includes a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103. The element layer 101 includesan insulating layer 205, a plurality of transistors, an insulating layer207, an insulating layer 209a, an insulating layer 209b, a plurality oflight-emitting elements, an insulating layer 211, an insulating layer217, a bonding layer 213, a coloring layer 259, a light-blocking layer257, a plurality of light-receiving elements, a conductive layer 280, aconductive layer 281, and an insulating layer 255.

FIG. 3B illustrates an example in which a light-receiving element isprovided between the insulating layer 205 and the bonding layer 213.Since the light-receiving element is provided between the insulatinglayer 205 and the bonding layer 213, a conductive layer to which thelight-receiving element is electrically connected and a photoelectricconversion layer included in the light-receiving element can be formedusing the same materials and the same steps as a conductive layer and asemiconductor layer included in the transistor 240. Thus, thelight-emitting device capable of touch operation can be manufacturedwithout a significant increase in the number of manufacturing steps.

The flexible substrate 103 and the flexible substrate 201 are preferablythe same as those in Specific Example 1.

Specific Example 4

FIG. 4A illustrates another example of a light-emitting device. Thelight-emitting device illustrated in FIG. 4A is capable of touchoperation.

The light-emitting device illustrated in FIG. 4A includes a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103. The element layer 101 includesan insulating layer 205, a plurality of transistors, a conductive layer156, a conductive layer 157, an insulating layer 207, an insulatinglayer 209, a plurality of light-emitting elements, an insulating layer211, an insulating layer 217, a bonding layer 213, a coloring layer 259,a light-blocking layer 257, an insulating layer 255, a conductive layer272, a conductive layer 274, an insulating layer 276, an insulatinglayer 278, a conductive layer 294, and a conductive layer 296.

FIG. 4A illustrates an example in which a capacitive touch sensor isprovided between the insulating layer 255 and the bonding layer 213. Thecapacitive touch sensor includes the conductive layer 272 and theconductive layer 274.

The conductive layer 156 and the conductive layer 157 are electricallyconnected to an FPC 108 via a connector 215. The conductive layer 294and the conductive layer 296 are electrically connected to theconductive layer 274 via conductive particles 292. Thus, the capacitivetouch sensor can be driven via the FPC 108.

The flexible substrate 103 and the flexible substrate 201 are preferablythe same as those in Specific Example 1.

Specific Example 5

FIG. 4B illustrates another example of a light-emitting device. Thelight-emitting device illustrated in FIG. 4B is capable of touchoperation.

The light-emitting device illustrated in FIG. 4B includes a flexiblesubstrate 201, a bonding layer 203, an element layer 101, a bondinglayer 105, and a flexible substrate 103. The element layer 101 includesan insulating layer 205, a plurality of transistors, a conductive layer156, a conductive layer 157, an insulating layer 207, an insulatinglayer 209, a plurality of light-emitting elements, an insulating layer211, an insulating layer 217, a bonding layer 213, a coloring layer 259,a light-blocking layer 257, an insulating layer 255, a conductive layer270, a conductive layer 272, a conductive layer 274, an insulating layer276, and an insulating layer 278.

FIG. 4B illustrates an example in which a capacitive touch sensor isprovided between the insulating layer 255 and the bonding layer 213. Thecapacitive touch sensor includes the conductive layer 272 and theconductive layer 274.

Note that the touch sensor may be provided over the flexible substrate103 as illustrated in FIG. 14A. Alternatively, a flexible substrate 102may be provided over the flexible substrate 103, and the touch sensormay be provided over the flexible substrate 102, as illustrated in FIG.14B. The flexible substrate 103 and the flexible substrate 102 areattached to each other with a bonding layer 204. A material similar tothat of the bonding layer 203 is preferably used for the bonding layer204. Accordingly, light reflection can be suppressed. In addition, theoccurrence of displacement at the time of bending the light-emittingdevice can be suppressed. Note that as in the structure illustrated inFIG. 4B, the insulating layer 255 and the bonding layer 105 may beprovided between the flexible substrate 103 and the conductive layer272.

The conductive layer 156 and the conductive layer 157 are electricallyconnected to an FPC 108a via a connector 215a. The conductive layer 270is electrically connected to an FPC 108b via a connector 215b. Thus, thelight-emitting element 230 and the transistor 240 can be driven via theFPC 108a, and the capacitive touch sensor can be driven via the FPC108b.

The flexible substrate 103 and the flexible substrate 201 are preferablythe same as those in Specific Example 1. The flexible substrate 102 canalso be the same. Note that in Specific Example 5, light emitted fromthe light-emitting element 230 is extracted through the flexiblesubstrate 103 (and the flexible substrate 102). Therefore, a materialwhich transmits visible light is used for each of the flexible substrate103 and the flexible substrate 102.

The same material is preferably used for the flexible substrate 102 andthe flexible substrate 103. Accordingly, the difference in thermalexpansion coefficient between the flexible substrate 102 and theflexible substrate 103 can be decreased. Furthermore, the same materialis preferably used for the flexible substrate 201. Accordingly, thedifference in thermal expansion coefficient between the flexiblesubstrate 102, the flexible substrate 103, and the flexible substrate201 can be decreased.

Specific Example 6

FIG. 5A illustrates another example of the light extraction portion 104in the light-emitting device.

The light-emitting device illustrated in FIG. 5A includes a flexiblesubstrate 103, a bonding layer 105, an element layer 101, a bondinglayer 213, and a flexible substrate 202. The element layer 101 includesan insulating layer 205, a plurality of transistors, an insulating layer207, a conductive layer 208, an insulating layer 209a, an insulatinglayer 209b, a plurality of light-emitting elements, an insulating layer211, and a coloring layer 259.

A light-emitting element 230 includes a lower electrode 231, an EL layer233, and an upper electrode 235. The lower electrode 231 is electricallyconnected to a source electrode or a drain electrode of a transistor 240via the conductive layer 208. An end portion of the lower electrode 231is covered with the insulating layer 211. The light-emitting element 230has a bottom emission structure. The lower electrode 231 has alight-transmitting property and transmits light emitted from the ELlayer 233.

The coloring layer 259 is provided to overlap with the light-emittingelement 230, and light emitted from the light-emitting element 230 isextracted from the flexible substrate 103 side through the coloringlayer 259. The space between the light-emitting element 230 and theflexible substrate 202 is filled with the bonding layer 213.

Note that the light-emitting device of one embodiment of the presentinvention may include the light-emitting element 230 which does notoverlap with the coloring layer 259 as illustrated in FIG. 5C. Forexample, in the case where one pixel includes four sub-pixels which arered, blue, green, and white sub-pixels, the coloring layer 259 is notnecessarily provided in the white sub-pixel. Accordingly, the amount oflight absorbed by the coloring layer can be reduced, and thus, the powerconsumption of the light-emitting device can be reduced. With the use ofdifferent materials for an EL layer 233a and an EL layer 233b,light-emitting elements exhibiting different colors may be manufacturedin pixels.

In Specific Example 6, light emitted from the light-emitting element 230is extracted through the flexible substrate 103. Therefore, a materialwhich transmits visible light is used for the flexible substrate 103.

It is also preferable that the absolute value of a difference in thermalexpansion coefficient between the flexible substrate 103 and theflexible substrate 202 be smaller than or equal to 10% of the thermalexpansion coefficient of the flexible substrate 103 or the flexiblesubstrate 202.

In the case where the flexible substrate 202 and the flexible substrate103 are in contact with each other on the outer side of the end portionof the element layer 101 as illustrated in FIG. 2C, 2D, or 2G, theadhesion can be increased by using materials having similar properties.This structure is preferable because an impurity such as atmosphericmoisture does not easily enter the element layer 101 and a decrease inreliability of the light-emitting device can be suppressed. Further, asillustrated in FIG. 2B, 2E, or 2F, the flexible substrate 202 and theflexible substrate 103 may be attached to each other with the bondinglayer 206, the bonding layer 105, or the like.

Specific Example 7

FIG. 5B illustrates another example of a light-emitting device.

The light-emitting device illustrated in FIG. 5B includes a flexiblesubstrate 103, a bonding layer 105, an element layer 101, a bondinglayer 213, and a flexible substrate 202. The element layer 101 includesan insulating layer 205, a conductive layer 310a, a conductive layer310b, a plurality of light-emitting elements, an insulating layer 211,and a conductive layer 212.

The conductive layer 310a and the conductive layer 310b, which areexternal connection electrodes of the light-emitting device, can each beelectrically connected to an FPC or the like.

A light-emitting element 230 includes a lower electrode 231, an EL layer233, and an upper electrode 235. An end portion of the lower electrode231 is covered with the insulating layer 211. The light-emitting element230 has a bottom emission structure. The lower electrode 231 has alight-transmitting property and transmits light emitted from the ELlayer 233. The conductive layer 212 is electrically connected to thelower electrode 231.

The flexible substrate 103 may have, as a light extraction structure, ahemispherical lens, a micro lens array, a film provided with an unevensurface structure, a light diffusing film, or the like. For example, theflexible substrate 103 with a light extraction structure can be formedby attaching the above lens or film to a resin substrate with anadhesive or the like having substantially the same refractive index asthe substrate or the lens or film.

The conductive layer 212 is preferably, though not necessarily, providedbecause voltage drop due to the resistance of the lower electrode 231can be prevented. In addition, for a similar purpose, a conductive layerelectrically connected to the upper electrode 235 may be provided overthe insulating layer 211, the EL layer 233, the upper electrode 235, orthe like.

The conductive layer 212 can be a single layer or a stacked layer formedusing a material selected from copper, titanium, tantalum, tungsten,molybdenum, chromium, neodymium, scandium, nickel, or aluminum, an alloymaterial containing any of these materials as its main component, or thelike. The thickness of the conductive layer 212 can be, for example,greater than or equal to 0.1 μm and less than or equal to 3 μm,preferably greater than or equal to 0.1 μm and less than or equal to 0.5μm.

When a paste (e.g., silver paste) is used as a material for theconductive layer electrically connected to the upper electrode 235,metal particles forming the conductive layer aggregate; therefore, thesurface of the conductive layer is rough and has many gaps. Thus, evenwhen the conductive layer is formed over the insulating layer 211, forexample, it is difficult for the EL layer 233 to completely cover theconductive layer; accordingly, the upper electrode and the conductivelayer are electrically connected to each other easily, which ispreferable.

The flexible substrate 103 and the flexible substrate 202 are preferablythe same as those in Specific Example 6.

Examples of Materials

Next, materials and the like that can be used for a light-emittingdevice are described. Note that description on the components alreadydescribed in this embodiment is omitted.

[Functional Element]

The element layer 101 includes at least a light-emitting element. As thelight-emitting element, a self-luminous element can be used, and anelement whose luminance is controlled by current or voltage is includedin the category of the light-emitting element. For example, alight-emitting diode (LED), an organic EL element, an inorganic ELelement, or the like can be used.

The element layer 101 may further include a transistor for driving thelight-emitting element, a touch sensor, or the like.

The structure of the transistors in the light-emitting device is notparticularly limited. For example, a forward staggered transistor or aninverted staggered transistor may be used. A top-gate transistor or abottom-gate transistor may be used. A semiconductor material used forthe transistors is not particularly limited, and for example, silicon orgermanium can be used. Alternatively, an oxide semiconductor containingat least one of indium, gallium, and zinc, such as an In—Ga—Zn-basedmetal oxide, may be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

The light-emitting element included in the light-emitting deviceincludes a pair of electrodes (the lower electrode 231 and the upperelectrode 235), and the EL layer 233 between the pair of electrodes. Oneof the pair of electrodes functions as an anode and the other functionsas a cathode.

The light-emitting element may have any of a top emission structure, abottom emission structure, and a dual emission structure. A conductivefilm that transmits visible light is used as the electrode through whichlight is extracted. A conductive film that reflects visible light ispreferably used as the electrode through which light is not extracted.

The conductive film that transmits visible light can be formed using,for example, indium oxide, indium tin oxide (ITO), indium zinc oxide,zinc oxide, or zinc oxide to which gallium is added. Alternatively, afilm of a metal material such as gold, silver, platinum, magnesium,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,or titanium; an alloy containing any of these metal materials; or anitride of any of these metal materials (e.g., titanium nitride) can beformed thin so as to have a light-transmitting property. Alternatively,a stacked film of any of the above materials can be used as theconductive film. For example, a stacked film of ITO and an alloy ofsilver and magnesium is preferably used, in which case conductivity canbe increased. Further alternatively, graphene or the like may be used.

For the conductive film that reflects visible light, for example, ametal material such as aluminum, gold, platinum, silver, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or analloy containing any of these metal materials can be used. Further,lanthanum, neodymium, germanium, or the like may be added to the metalmaterial or the alloy. Furthermore, an alloy containing aluminum (analuminum alloy) such as an alloy of aluminum and titanium, an alloy ofaluminum and nickel, or an alloy of aluminum and neodymium; or an alloycontaining silver such as an alloy of silver and copper, an alloy ofsilver, copper, and palladium, or an alloy of silver and magnesium canbe used for the conductive film. An alloy of silver and copper ispreferable because of its high heat resistance. Further, when a metalfilm or a metal oxide film is stacked on and in contact with an aluminumalloy film, oxidation of the aluminum alloy film can be prevented.Examples of a material for the metal film or the metal oxide filminclude titanium and titanium oxide. Alternatively, the above conductivefilm that transmits visible light and a film containing a metal materialmay be stacked. For example, a stacked film of silver and ITO or astacked film of an alloy of silver and magnesium and ITO can be used.

Each of the electrodes can be formed by an evaporation method or asputtering method. Alternatively, a discharging method such as an inkjetmethod, a printing method such as a screen printing method, or a platingmethod may be used.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the lower electrode 231 and the upperelectrode 235, holes are injected to the EL layer 233 from the anodeside and electrons are injected to the EL layer 233 from the cathodeside. The injected electrons and holes are recombined in the EL layer233 and a light-emitting substance contained in the EL layer 233 emitslight.

The EL layer 233 includes at least a light-emitting layer. In additionto the light-emitting layer, the EL layer 233 may further include one ormore layers containing any of a substance with a high hole-injectionproperty, a substance with a high hole-transport property, ahole-blocking material, a substance with a high electron-transportproperty, a substance with a high electron-injection property, asubstance with a bipolar property (a substance with a high electron- andhole-transport property), and the like.

For the EL layer 233, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may also beused. Each of the layers included in the EL layer 233 can be formed byany of the following methods: an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an inkjetmethod, a coating method, and the like.

In the element layer 101, the light-emitting element is preferablyprovided between a pair of insulating films with low water permeability.In that case, an impurity such as water can be prevented from enteringthe light-emitting element, leading to prevention of a decrease in thereliability of the light-emitting device.

As an insulating film with low water permeability, a film containingnitrogen and silicon (e.g., a silicon nitride film or a siliconoxynitride film), a film containing nitrogen and aluminum (e.g., analuminum nitride film), or the like can be used. Alternatively, asilicon oxide film, a silicon oxynitride film, an aluminum oxide film,or the like can be used.

For example, the water vapor transmittance of the insulating film withlow water permeability is lower than or equal to 1×10⁻⁵ [g/m²·day],preferably lower than or equal to 1×10⁻⁶ [g/m²·day], further preferablylower than or equal to 1×10⁻⁷ [g/m²·day], still further preferably lowerthan or equal to 1×10⁻⁸ [g/m²·day].

[Bonding Layer]

For the bonding layer, any of a variety of types of curable adhesives,e.g., a light curable adhesive such as a UV curable adhesive, a reactivecurable adhesive, a heat curable adhesive, and an anaerobic adhesive canbe used. Examples of these adhesives include an epoxy resin, an acrylicresin, a silicone resin, a phenol resin, a polyimide resin, an imideresin, a polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB)resin, an ethylene vinyl acetate (EVA) resin, and the like. Inparticular, a material with low moisture permeability, such as an epoxyresin, is preferred. Alternatively, a two-component type resin may beused. Still alternatively, a bonding sheet or the like may be used.

Further, the resin may include a drying agent. For example, a substancethat adsorbs moisture by chemical adsorption, such as oxide of analkaline earth metal (e.g., calcium oxide or barium oxide), can be used.Alternatively, a substance that adsorbs moisture by physical adsorption,such as zeolite or silica gel, may be used. The drying agent ispreferably included because it can prevent an impurity such as moisturefrom entering the light-emitting element, thereby improving thereliability of the light-emitting device.

The bonding layer 105 has a light-transmitting property and transmits atleast light emitted from the light-emitting element included in theelement layer 101. The refractive index of the bonding layer 105 ishigher than that of the air.

In addition, it is preferable to mix a filler with a high refractiveindex (e.g., titanium oxide) into the resin, in which case theefficiency of light extraction from the light-emitting element can beimproved. Accordingly, assuming that power consumption is the same,luminance can be increased. Furthermore, assuming that luminance is thesame, power consumption can be decreased.

The bonding layer 105 may also include a scattering member forscattering light. For example, the bonding layer 105 can be a mixture ofthe above resin and particles having a refractive index different fromthat of the resin. The particles function as the scattering member forscattering light.

The difference in refractive index between the resin and the particleswith a refractive index different from that of the resin is preferably0.1 or more, further preferably 0.3 or more. Specifically, an epoxyresin, an acrylic resin, an imide resin, silicone, or the like can beused as the resin, and titanium oxide, barium oxide, zeolite, or thelike can be used as the particles.

Particles of titanium oxide or barium oxide are preferable because theyscatter light excellently. When zeolite is used, it can adsorb watercontained in the resin and the like, thereby improving the reliabilityof the light-emitting element.

In the case where light emitted from the light-emitting element isextracted through the bonding layer 213, the bonding layer 213 can bethe same as the bonding layer 105 described above.

[Insulating Layer]

The insulating layer 205 and the insulating layer 255 can each be formedusing an inorganic insulating material. It is particularly preferable touse the insulating film with low water permeability, in which case ahighly reliable light-emitting device can be provided.

The insulating layer 207 has an effect of preventing diffusion ofimpurities into a semiconductor included in the transistor. As theinsulating layer 207, an inorganic insulating film such as a siliconoxide film, a silicon oxynitride film, a silicon nitride film, a siliconnitride oxide film, or an aluminum oxide film can be used.

As each of the insulating layers 209, 209a, and 209b, an insulating filmwith a planarization function is preferably selected in order to reducesurface unevenness due to the transistor or the like. For example, anorganic material such as a polyimide resin, an acrylic resin, or abenzocyclobutene-based resin can be used. Other than such organicmaterials, it is also possible to use a low-dielectric constant material(a low-k material) or the like. Note that the planarization insulatingfilm may have a stacked structure of any of insulating films formed ofthese materials and inorganic insulating films.

The insulating layer 211 is provided to cover an end portion of thelower electrode 231. In order that the insulating layer 211 be favorablycovered with the EL layer 233 and the upper electrode 235 formedthereover, a side wall of the insulating layer 211 preferably has atilted surface with continuous curvature.

As a material for the insulating layer 211, a resin or an inorganicinsulating material can be used. As the resin, for example, a polyimideresin, a polyamide resin, an acrylic resin, a siloxane resin, an epoxyresin, or a phenol resin can be used. In particular, either a negativephotosensitive resin or a positive photosensitive resin is preferablyused for easy formation of the insulating layer 211.

There is no particular limitation on the method for forming theinsulating layer 211; a photolithography method, a sputtering method, anevaporation method, a droplet discharging method (e.g., an inkjetmethod), a printing method (e.g., a screen printing method or an off-setprinting method), or the like may be used.

The insulating layer 217 can be formed using an inorganic insulatingmaterial, an organic insulating material, or the like. As the organicinsulating material, for example, a negative or positive photosensitiveresin, a non-photosensitive resin, or the like can be used. Instead ofthe insulating layer 217, a conductive layer may be formed. For example,the conductive layer can be formed using a metal material such astitanium or aluminum. When a conductive layer is used instead of theinsulating layer 217 and the conductive layer is electrically connectedto the upper electrode 235, voltage drop due to the resistance of theupper electrode 235 can be prevented. The insulating layer 217 may haveeither a tapered shape or an inverse tapered shape.

Each of the insulating layers 276, 278, 291, 293, and 295 can be formedusing an inorganic insulating material or an organic insulatingmaterial. It is particularly preferable to use an insulating layer witha planarization function for each of the insulating layers 278 and 295in order to reduce surface unevenness due to a sensor element.

[Conductive Layer]

Each of the conductive layers 156, 157, 294, and 296 can be formed usingthe same material and the same step as a conductive layer included inthe transistor or the light-emitting element. The conductive layer 280can be formed using the same material and the same step as a conductivelayer included in the transistor.

For example, each of the conductive layers can be formed to have asingle-layer structure or a stacked-layer structure using any of metalmaterials such as molybdenum, titanium, chromium, tantalum, tungsten,aluminum, copper, neodymium, and scandium, and an alloy materialcontaining any of these elements. Each of the conductive layers may beformed using a conductive metal oxide. As the conductive metal oxide,indium oxide (e.g., In₂O₃), tin oxide (e.g., SnO₂), zinc oxide (ZnO),ITO, indium zinc oxide (e.g., In₂O₃—ZnO), or any of these metal oxidematerials in which silicon oxide is contained can be used.

Each of the conductive layers 208, 212, 310a, and 310b can also beformed using any of the above metal materials, alloy materials, andconductive metal oxides.

Each of the conductive layers 272, 274, 281, and 283 is a conductivelayer with a light-transmitting property. The conductive layer can beformed using, for example, indium oxide, ITO, indium zinc oxide, zincoxide, zinc oxide to which gallium is added, or the like. The conductivelayer 270 can be formed using the same material and the same step as theconductive layer 272.

As the conductive particles 292, particles of an organic resin, silica,or the like coated with a metal material are used. It is preferable touse nickel or gold as the metal material because contact resistance canbe reduced. It is also preferable to use particles each coated withlayers of two or more kinds of metal materials, such as particles coatedwith nickel and further with gold.

For the connector 215, it is possible to use a paste-like or sheet-likematerial which is obtained by mixture of metal particles and aheat-curable resin and for which anisotropic electric conductivity isprovided by thermocompression bonding. As the metal particles, particlesin which two or more kinds of metals are layered, for example, nickelparticles coated with gold, are preferably used.

[Coloring Layer, Light-Blocking Layer, and Overcoat]

The coloring layer 259 is a coloring layer that transmits light in aspecific wavelength range. For example, a red (R) color filter fortransmitting light in a red wavelength range, a green (G) color filterfor transmitting light in a green wavelength range, a blue (B) colorfilter for transmitting light in a blue wavelength range, or the likecan be used. Each coloring layer is formed in a desired position withany of various materials by a printing method, an inkjet method, anetching method using a photolithography method, or the like.

The light-blocking layer 257 is provided between the adjacent coloringlayers 259. The light-blocking layer 257 blocks light emitted from theadjacent light-emitting element, thereby preventing color mixturebetween adjacent pixels. Here, the coloring layer 259 is provided suchthat its end portion overlaps with the light-blocking layer 257, wherebylight leakage can be prevented. The light-blocking layer 257 can beformed using a material that blocks light emitted from thelight-emitting element, for example, a metal material, a resin materialincluding a pigment or a dye, or the like. Note that as illustrated inFIG. 1C, the light-blocking layer 257 is preferably provided also in aregion other than the light extraction portion 104, such as the drivercircuit portion 106, in which case undesired leakage of guided light orthe like can be prevented.

The overcoat 261 may be provided to cover the coloring layer 259 and thelight-blocking layer 257. With the overcoat, impurities and the likecontained in the coloring layer can be prevented from being diffusedinto an organic EL element. The overcoat is formed with a material thattransmits light emitted from the organic EL element; for example, aninorganic insulating film such as a silicon nitride film or a siliconoxide film, an organic insulating film such as an acrylic film or apolyimide film can be used, and further, a stacked structure of anorganic insulating film and an inorganic insulating film may beemployed. The insulating film with low water permeability may be usedfor the overcoat 261.

In the case where a material of the bonding layer 213 is applied to thecoloring layer 259 and the light-blocking layer 257, a material withhigh wettability with respect to the material of the bonding layer 213is preferably used as a material of the overcoat 261. For example, anoxide conductive film such as an ITO film or a metal film such as an Agfilm which is thin enough to transmit light is preferably used.

Example of Manufacturing Method

Next, an example of a method for manufacturing a light-emitting devicewill be described with reference to FIGS. 6A to 6C and FIGS. 7A to 7C.Here, the manufacturing method is described using the light-emittingdevice of Specific Example 1 (FIG. 1C) as an example.

First, a separation layer 303 is formed over a formation substrate 301,and the insulating layer 205 is formed over the separation layer 303.Next, the plurality of transistors, the conductive layer 157, theinsulating layer 207, the insulating layer 209, the plurality oflight-emitting elements, and the insulating layer 211 are formed overthe insulating layer 205. An opening is formed in the insulating layers211, 209, and 207 to expose the conductive layer 157 (FIG. 6A).

In addition, a separation layer 307 is formed over a formation substrate305, and the insulating layer 255 is formed over the separation layer307. Next, the light-blocking layer 257, the coloring layer 259, and theovercoat 261 are formed over the insulating layer 255 (FIG. 6B).

The formation substrate 301 and the formation substrate 305 can each bea glass substrate, a quartz substrate, a sapphire substrate, a ceramicsubstrate, a metal substrate, or the like.

For the glass substrate, for example, a glass material such asaluminosilicate glass, aluminoborosilicate glass, or barium borosilicateglass can be used. When the temperature of heat treatment performedlater is high, a substrate having a strain point of 730° C. or higher ispreferably used. Note that when containing a large amount of bariumoxide (BaO), the glass substrate can be heat-resistant and morepractical. Alternatively, crystallized glass or the like may be used.

In the case where a glass substrate is used as the formation substrate,an insulating film such as a silicon oxide film, a silicon oxynitridefilm, a silicon nitride film, or a silicon nitride oxide film ispreferably formed between the formation substrate and the separationlayer, in which case contamination from the glass substrate can beprevented.

The separation layer 303 and the separation layer 307 each have asingle-layer structure or a stacked-layer structure containing anelement selected from tungsten, molybdenum, titanium, tantalum, niobium,nickel, cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium,iridium, and silicon; an alloy material containing any of the elements;or a compound material containing any of the elements. A crystalstructure of a layer containing silicon may be amorphous, microcrystal,or polycrystal.

The separation layer can be formed by a sputtering method, a plasma CVDmethod, a coating method, a printing method, or the like. Note that acoating method includes a spin coating method, a droplet dischargemethod, and a dispensing method.

In the case where the separation layer has a single-layer structure, atungsten layer, a molybdenum layer, or a layer containing a mixture oftungsten and molybdenum is preferably formed. Alternatively, a layercontaining an oxide or an oxynitride of tungsten, a layer containing anoxide or an oxynitride of molybdenum, or a layer containing an oxide oran oxynitride of a mixture of tungsten and molybdenum may be formed.Note that the mixture of tungsten and molybdenum corresponds to an alloyof tungsten and molybdenum, for example.

In the case where the separation layer is formed to have a stacked-layerstructure including a layer containing tungsten and a layer containingan oxide of tungsten, the layer containing an oxide of tungsten may beformed as follows: the layer containing tungsten is formed first and aninsulating film formed of an oxide is formed thereover, so that thelayer containing an oxide of tungsten is formed at the interface betweenthe tungsten layer and the insulating film. Alternatively, the layercontaining an oxide of tungsten may be formed by performing thermaloxidation treatment, oxygen plasma treatment, nitrous oxide (N₂O) plasmatreatment, treatment with a highly oxidizing solution such as ozonewater, or the like on the surface of the layer containing tungsten.Plasma treatment or heat treatment may be performed in an atmosphere ofoxygen, nitrogen, or nitrous oxide alone, or a mixed gas of any of thesegasses and another gas. Surface condition of the separation layer ischanged by the plasma treatment or heat treatment, whereby adhesionbetween the separation layer and the insulating layer formed later canbe controlled.

Each of the insulating layers can be formed by a sputtering method, aplasma CVD method, a coating method, a printing method, or the like. Forexample, the insulating layer is formed at a temperature of higher thanor equal to 250° C. and lower than or equal to 400° C. by a plasma CVDmethod, whereby the insulating layer can be a dense film with very lowwater permeability.

Then, a material for the bonding layer 213 is applied to a surface ofthe formation substrate 305 over which the coloring layer 259 and thelike are formed or a surface of the formation substrate 301 over whichthe light-emitting element 230 and the like are formed, and theformation substrate 301 and the formation substrate 305 are attached sothat these two surfaces face each other with the bonding layer 213positioned therebetween (FIG. 6C).

Next, the formation substrate 301 is separated, and the exposedinsulating layer 205 and the flexible substrate 201 are attached to eachother with the bonding layer 203. Further, the formation substrate 305is separated, and the exposed insulating layer 255 and the flexiblesubstrate 103 are attached to each other with the bonding layer 105.Although the flexible substrate 103 does not overlap with the conductivelayer 157 in FIG. 7A, the flexible substrate 103 may overlap with theconductive layer 157.

Any of a variety of methods can be used as appropriate for theseparation process. For example, when a layer including a metal oxidefilm is formed as the separation layer on the side in contact with thelayer to be separated, the metal oxide film is embrittled bycrystallization, whereby the layer to be separated can be separated fromthe formation substrate. Alternatively, when an amorphous silicon filmcontaining hydrogen is formed as the separation layer between theformation substrate having high heat resistance and the layer to beseparated, the amorphous silicon film is removed by laser lightirradiation or etching, whereby the layer to be separated can beseparated from the formation substrate. Alternatively, after a layerincluding a metal oxide film is formed as the separation layer on theside in contact with the layer to be separated, the metal oxide film isembrittled by crystallization, and part of the separation layer isremoved by etching using a solution or a fluoride gas such as NF₃, BrF₃,or ClF₃, whereby the separation can be performed at the embrittled metaloxide film. Furthermore, a method may be used in which a film containingnitrogen, oxygen, hydrogen, or the like (for example, an amorphoussilicon film containing hydrogen, an alloy film containing hydrogen, analloy film containing oxygen, or the like) is used as the separationlayer, and the separation layer is irradiated with laser light torelease the nitrogen, oxygen, or hydrogen contained in the separationlayer as a gas, thereby promoting separation between the layer to beseparated and the formation substrate. Alternatively, it is possible touse a method in which the formation substrate provided with the layer tobe separated is removed mechanically or by etching using a solution or afluoride gas such as NF₃, BrF₃, or ClF₃, or the like. In this case, theseparation layer is not necessarily provided.

Further, the separation process can be conducted easily by combinationof the above-described separation methods. In other words, separationcan be performed with physical force (by a machine or the like) afterperforming laser light irradiation, etching on the separation layer witha gas, a solution, or the like, or mechanical removal with a sharpknife, scalpel or the like so that the separation layer and the layer tobe separated can be easily separated from each other.

Separation of the layer to be separated from the formation substrate maybe carried out by filling the interface between the separation layer andthe layer to be separated with a liquid. Further, the separation may beconducted while pouring a liquid such as water.

As another separation method, in the case where the separation layer isformed using tungsten, it is preferable that the separation be performedwhile etching the separation layer using a mixed solution of ammoniawater and a hydrogen peroxide solution.

Note that the separation layer is not necessary in the case whereseparation at the interface between the formation substrate and thelayer to be separated is possible. For example, glass is used as theformation substrate, an organic resin such as polyimide, polyester,polyolefin, polyamide, polycarbonate, or acrylic is formed in contactwith the glass, and an insulating film, a transistor, and the like areformed over the organic resin. In this case, heating the organic resinenables the separation at the interface between the formation substrateand the organic resin. Alternatively, separation at the interfacebetween a metal layer and the organic resin may be performed in thefollowing manner: the metal layer is provided between the formationsubstrate and the organic resin and current is made to flow in the metallayer so that the metal layer is heated. In that case, the organic resincan be used as a substrate of the light-emitting device. Furthermore,the organic resin and another substrate may be attached to each otherwith an adhesive.

Lastly, an opening is formed in the insulating layer 255 and the bondinglayer 213 to expose the conductive layer 157 (FIG. 7B). In the casewhere the flexible substrate 103 overlaps with the conductive layer 157,the opening is formed also in the flexible substrate 103 and the bondinglayer 105 so that the conductive layer 157 is exposed (FIG. 7C). Themethod for forming the opening is not particularly limited and may be,for example, a laser ablation method, an etching method, an ion beamsputtering method, or the like. As another method, a cut may be made ina film over the conductive layer 157 with a sharp knife or the like andpart of the film may be separated by physical force.

In the above-described manner, the light-emitting device can bemanufactured.

As described above, the light-emitting device of this embodimentincludes two substrates: one is the flexible substrate 103 and the otheris the flexible substrate 201 or the flexible substrate 202. Thelight-emitting device can be formed with two substrates even whenincluding a touch sensor. Owing to the use of the minimum number ofsubstrates, improvement in light extraction efficiency and improvementin clarity of display can be easily achieved. Accordingly, assuming thatpower consumption is the same, luminance can be increased. Furthermore,assuming that luminance is the same, power consumption can be decreased.

Note that the light-emitting device including the light-emitting elementis described in this embodiment as an example; however, one embodimentof the present invention is not limited to this example. A variety ofsemiconductor devices and a variety of display devices can be given asexamples of devices in which flexible substrates that are a feature ofone embodiment of the present invention can be used. For example,flexible substrates that are a feature of one embodiment of the presentinvention can be used as substrates in the following elements ordevices. Examples include an EL element (e.g., an EL element includingorganic and inorganic materials, an organic EL element, or an inorganicEL element), an LED (e.g., a white LED, a red LED, a green LED, or ablue LED), a transistor (a transistor which emits light depending oncurrent), an electron emitter, a liquid crystal element, electronic ink,an electrophoretic element, a grating light valve (GLV), a plasmadisplay panel (PDP), a micro electro mechanical system (MEMS), a digitalmicromirror device (DMD), a digital micro shutter (DMS), MIRASOL(registered trademark), an interferometic modulator display (IMOD), anelectrowetting element, a piezoelectric ceramic display, or a carbonnanotube, which are display media whose contrast, luminance,reflectivity, transmittance, or the like is changed by electromagneticaction. Examples further include a display device having electronemitters, such as a field emission display (FED) or an SED-type flatpanel display (SED: surface-conduction electron-emitter display).Examples further include a display device having a liquid crystalelement, such as a liquid crystal display (e.g., a transmissive liquidcrystal display, a transflective liquid crystal display, a reflectiveliquid crystal display, a direct-view liquid crystal display, or aprojection liquid crystal display). Examples further include a displaydevice including electronic ink or electrophoretic elements, such aselectronic paper.

Display of electronic paper can be performed using, for example,molecules (a method utilizing optical anisotropy, dye molecularorientation, or the like), particles (a method utilizingelectrophoresis, particle movement, particle rotation, phase change, orthe like), movement of one end of a film, coloring properties or phasechange of molecules, optical absorption by molecules, or self-lightemission by combination of electrons and holes. Specific examples of adisplay method of electronic paper include microcapsule electrophoresis,horizontal electrophoresis, vertical electrophoresis, a sphericaltwisting ball, a magnetic twisting ball, a columnar twisting ball, acharged toner, electronic liquid powder, magnetic electrophoresis, amagnetic thermosensitive type, electro wetting, light-scattering(transparent-opaque change), a cholesteric liquid crystal and aphotoconductive layer, cholesteric liquid crystal, bistable nematicliquid crystal, ferroelectric liquid crystal, a liquid crystal dispersedtype with a dichroic dye, a movable film, coloring and decoloringproperties of a leuco dye, photochromism, electrochromism,electrodeposition, and flexible organic EL. Note that one embodiment ofthe present invention is not limited to these examples, and variouselectronic paper and display methods can be used as electronic paper anda display method thereof. Here, with the use of microcapsuleelectrophoresis, aggregation and precipitation of electrophoreticparticles can be prevented. Electronic liquid powder has advantages suchas high-speed response, high reflectivity, wide viewing angle, low powerconsumption, and memory properties.

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 2

In this embodiment, electronic devices to which one embodiment of thepresent invention is applied will be described with reference to FIGS.8A to 8C, FIG. 9, FIGS. 10A to 10E, and FIGS. 11A to 11C.

An electronic device of this embodiment includes a strip-like highflexibility region and a strip-like low flexibility region that arearranged alternately. The electronic device can be folded by bending thehigh flexibility region. The electronic device of this embodiment ishighly portable in a folded state, and is highly browsable in an openedstate because of a seamless large light-emitting region.

In the electronic device of this embodiment, the high flexibility regioncan be bent either inward or outward.

Note that in this specification, being “bent inward” means being bentsuch that a light-emitting surface of a light-emitting device facesinward, and being “bent outward” means being bent such that alight-emitting surface of a light-emitting device faces outward. Alight-emitting surface of an electronic device or a light-emittingdevice refers to a surface through which light emitted from alight-emitting element is extracted.

When the electronic device of this embodiment is not in use, it can befolded such that a light-emitting surface of a light-emitting devicefaces inward, whereby the light-emitting surface can be prevented frombeing damaged or contaminated.

When the electronic device of this embodiment is in use, it can beopened so that the seamless large light-emitting region is entirelyused, or it can be folded such that the light-emitting surface of thelight-emitting device faces outward and the light-emitting region can bepartly used. Folding the electronic device and putting part of thelight-emitting region that is hidden from a user in a non-light-emittingstate can reduce the power consumption of the electronic device.

An electronic device that can be folded in three parts and includes twostrip-like high flexibility regions and three strip-like low flexibilityregions is described below as an example.

FIG. 8A illustrates the electronic device that is opened. FIG. 8Billustrates the electronic device that is being opened or being folded.FIG. 8C illustrates the electronic device that is folded. FIG. 9 is aperspective view illustrating components of the electronic device. FIG.10A is a plan view of the light-emitting surface side of the electronicdevice, and FIG. 10B is a plan view of the side opposite to thelight-emitting surface side of the electronic device. FIGS. 10C and 10Dare examples of a side view of the electronic device in FIG. 10A that isviewed in the direction indicated by an arrow. FIG. 10E is across-sectional view taken along dashed-dotted line A-B in FIG. 10A.

The electronic device in FIGS. 8A to 8C includes a flexiblelight-emitting device 11. As the light-emitting device 11, thelight-emitting device of one embodiment of the present invention whichis described in Embodiment 1 can be used. The light-emitting device ofone embodiment of the present invention can be folded, for example, witha radius of curvature greater than or equal to 1 mm and less than orequal to 100 mm and can thus be suitably used in an electronic devicethat is configured to be folded once or more by inward or outwardbending.

The electronic device in FIGS. 8A to 8C further includes a plurality ofsupport panels 15a and a plurality of support panels 15b. Each of thesupport panels 15a and 15b has a lower flexibility than that of thelight-emitting device 11. The plurality of support panels 15a are apartfrom each other. The plurality of support panels 15b are apart from eachother.

As illustrated in FIG. 10A, the electronic device includes highflexibility regions E1 and low flexibility regions E2 that are arrangedalternately. The high flexibility region and the low flexibility regionare strip-like regions (form stripes). In this embodiment, a pluralityof high flexibility regions and a plurality of low flexibility regionsare parallel to each other; however, the regions are not necessarilyarranged parallel to each other.

The high flexibility region E1 in the electronic device includes atleast a flexible light-emitting device. A light-emitting device usingorganic EL elements is particularly preferable because it not only hashigh flexibility and impact resistance but also can be thinned andlightened.

The low flexibility region E2 in the electronic device includes at leasta flexible light-emitting device and a support panel having a lowerflexibility than that of the light-emitting device and overlapping withthe light-emitting device.

The support panel is provided on at least one of the light-emittingsurface side and the side opposite to the light-emitting surface side ofthe light-emitting device.

The light-emitting device preferably has support panels on both thelight-emitting surface side and the side opposite to the light-emittingsurface side, like the support panels 15a and 15b illustrated in FIG.10C, in which case the light-emitting device can be sandwiched between apair of support panels; thus, the mechanical strength of the lowflexibility region is increased and the electronic device becomes lesslikely to be broken.

Alternatively, a support panel 15 illustrated in FIG. 10D may be usedinstead of the support panels 15a and 15b and the light-emitting device11 may be held by the support panel 15.

It is preferable that the light-emitting device have the support panelon only one of the light-emitting surface side and the side opposite tothe light-emitting surface side because the electronic device can bethinner or more lightweight. For example, an electronic device thatincludes the plurality of support panels 15b and does not include theplurality of support panels 15a may be employed.

The high flexibility region E1 and the low flexibility region E2preferably include the light-emitting device and a protective layerhaving a higher flexibility than that of the support panel andoverlapping with the light-emitting device. In that case, the highflexibility region E1 in the electronic device can have high mechanicalstrength as well as flexibility and the electronic device becomes lesslikely to be broken. This structure makes the electronic device lesslikely to be broken by deformation due to external force or the like inthe high flexibility region.

For example, it is preferable that the support panel be the thickest andthe light-emitting device be the thinnest among the light-emittingdevice, the support panel, and the protective layer. Alternatively, forexample, it is preferable that the support panel have the lowestflexibility and the light-emitting device have the highest flexibilityamong the light-emitting device, the support panel, and the protectivelayer. Such a structure increases the difference in flexibility betweenthe high flexibility region and the low flexibility region. Thus, theelectronic device can be folded reliably at the high flexibility region,so that the low flexibility region is prevented from being bent.Consequently, the reliability of the electronic device can be improved.Such a structure also prevents the electronic device from being bent atan undesired portion.

The light-emitting device preferably has protective layers on both thelight-emitting surface side and the side opposite to the light-emittingsurface side, in which case the light-emitting device can be sandwichedbetween a pair of protective layers; thus, the electronic device hasincreased mechanical strength and becomes less likely to be broken.

For example, as illustrated in FIG. 10C, in the low flexibility regionE2, it is preferable that a pair of protective layers 13a and 13b beplaced between the pair of support panels 15a and 15b and thelight-emitting device (not illustrated) be placed between the pair ofprotective layers 13a and 13b.

Alternatively, as illustrated in FIG. 10D, in the low flexibility regionE2, it is preferable that the pair of protective layers 13a and 13b beheld by the support panel 15 and the light-emitting device (notillustrated) be placed between the pair of protective layers 13a and13b.

It is preferable that the light-emitting device have the protectivelayer on only one of the light-emitting surface side and the sideopposite to the light-emitting surface side because the electronicdevice can be thinner or more lightweight. For example, an electronicdevice that includes the protective layer 13b and does not include theprotective layer 13a may be employed.

When the protective layer 13a on the light-emitting surface side of thelight-emitting device is a light-blocking film, a non-light-emittingregion of the light-emitting device can be prevented from beingirradiated with external light. This structure is preferable because itprevents photodegradation of a transistor and the like of a drivercircuit that is included in the non-light-emitting region.

As illustrated in FIG. 10E, an opening in the protective layer 13aprovided on the light-emitting surface side of the light-emitting device11 overlaps with a light-emitting region 11a of the light-emittingdevice. The protective layer 13a overlaps with a non-light-emittingregion 11b that surrounds the light-emitting region 11a like a frame.The protective layer 13b provided on the side opposite to thelight-emitting surface side of the light-emitting device 11 overlapswith the light-emitting region 11a and the non-light-emitting region11b. The protective layer 13b is provided in a large region, preferablyon the entire surface on the side opposite to the light-emitting surfaceside to strongly protect the light-emitting device; thus, thereliability of the electronic device can be improved.

The protective layer and the support panel can be formed using plastic,a metal, an alloy, rubber, or the like. Plastic, rubber, or the like ispreferably used because it can form a protective layer or a supportpanel that is lightweight and less likely to be broken. For example,silicone rubber may be used for the protective layer and stainless steelor aluminum may be used for the support panel.

The protective layer and the support panel are preferably formed using amaterial with high toughness. In that case, an electronic device withhigh impact resistance that is less likely to be broken can be provided.For example, when an organic resin, a thin metal material, or a thinalloy material is used for the protective layer and the support panel,the electronic device can be lightweight and less likely to be broken.For a similar reason, also a substrate of the light-emitting device ispreferably formed using a material with high toughness.

The protective layer and the support panel on the light-emitting surfaceside do not necessarily have a light-transmitting property if they donot overlap with the light-emitting region of the light-emitting device.When the protective layer and the support panel on the light-emittingsurface side overlap with at least part of the light-emitting region,they are preferably formed using a material that transmits light emittedfrom the light-emitting device. There is no limitation on thelight-transmitting property of the protective layer and the supportpanel on the side opposite to the light-emitting surface side.

When any two of the protective layer, the support panel, and thelight-emitting device are bonded to each other, any of a variety ofadhesives can be used, and for example, a curable resin that is curableat room temperature (e.g., a two-component-mixture-type resin), a lightcurable resin, a heat curable resin, or the like can be used.Alternatively, a sheet-like adhesive may be used. Alternatively,components of the electronic device may be fixed with, for example, ascrew that penetrates two or more of the protective layer, the supportpanel, and the light-emitting device or a pin or clip that holds them.

The electronic device of this embodiment can be used with onelight-emitting device (one light-emitting region) divided into two ormore regions at a folded portion(s). For example, it is possible to putthe region that is hidden by folding the electronic device in anon-light-emitting state and put only the exposed region in alight-emitting state. Thus, power consumed by a region that is not usedby a user can be reduced.

The electronic device of this embodiment may include a sensor fordetermining whether each high flexibility region is bent or not. Thesensor can be composed of, for example, a switch, a MEMS pressuresensor, a pressure sensor, or the like.

In the examples described above, the electronic device includes two highflexibility regions; however, one embodiment of the present invention isnot limited thereto. For example, as illustrated in FIG. 11A, theelectronic device includes at least one high flexibility region E1.Embodiments of the present invention also include an electronic devicethat includes three high flexibility regions E1 and can be folded infour parts (FIG. 11B) and an electronic device that includes four highflexibility regions E1 and can be folded in five parts (FIG. 11C).

This embodiment can be combined with any of the other embodiments asappropriate.

Embodiment 3

In this embodiment, electronic devices and lighting devices to which oneembodiment of the present invention is applied will be described withreference to FIGS. 12A to 12G.

Electronic devices and lighting devices can have high reliability whenmanufactured using the light-emitting device of one embodiment of thepresent invention. Highly reliable flexible electronic devices andhighly reliable flexible lighting devices can be manufactured byadopting the light-emitting device of one embodiment of the presentinvention.

Examples of electronic devices are television devices (also referred toas TV or television receivers), monitors for computers and the like,cameras such as digital cameras and digital video cameras, digital photoframes, cellular phones (also referred to as portable telephonedevices), portable game machines, portable information terminals, audioplayback devices, large game machines such as pin-ball machines, and thelike.

The light-emitting device of one embodiment of the present invention hasflexibility and thus can be incorporated along a curved inside/outsidewall surface of a house or a building or a curved interior/exteriorsurface of a car.

FIG. 12A illustrates an example of a cellular phone. A cellular phone7400 is provided with a display portion 7402 incorporated in a housing7401, operation buttons 7403, an external connection port 7404, aspeaker 7405, a microphone 7406, and the like. Note that the cellularphone 7400 is manufactured using the light-emitting device of oneembodiment of the present invention in the display portion 7402. Inaccordance with one embodiment of the present invention, a highlyreliable cellular phone having a curved display portion can be providedat a high yield.

When the display portion 7402 of the cellular phone 7400 illustrated inFIG. 12A 10 is touched with a finger or the like, data can be input tothe cellular phone 7400. Further, operations such as making a call andinputting a character can be performed by touch on the display portion7402 with a finger or the like.

The power can be turned on or off with the operation button 7403. Inaddition, types of images displayed on the display portion 7402 can beswitched; for example, switching images from a mail creation screen to amain menu screen is performed with the operation button 7403.

FIG. 12B is an example of a wristband-type portable display device. Aportable display device 7100 includes a housing 7101, a display portion7102, an operation button 7103, and a sending and receiving device 7104.

The portable display device 7100 can receive a video signal with thesending and receiving device 7104 and can display the received video onthe display portion 7102. In addition, with the sending and receivingdevice 7104, the portable display device 7100 can send an audio signalto another receiving device.

With the operation button 7103, power ON/OFF, switching displayedvideos, adjusting volume, and the like can be performed.

Here, the display portion 7102 includes the light-emitting device of oneembodiment of the present invention. In accordance with one embodimentof the present invention, a highly reliable portable display devicehaving a curved display portion can be provided at a high yield.

FIGS. 12C to 12E illustrate examples of lighting devices. Lightingdevices 7200, 7210, and 7220 each include a stage 7201 provided with anoperation switch 7203 and a light-emitting portion supported by thestage 7201.

The lighting device 7200 illustrated in FIG. 12C includes alight-emitting portion 7202 with a wave-shaped light-emitting surfaceand thus is a good-design lighting device.

A light-emitting portion 7212 included in the lighting device 7210illustrated in FIG. 12D has two convex-curved light-emitting portionssymmetrically placed. Thus, light radiates from the lighting device7210.

The lighting device 7220 illustrated in FIG. 12E includes aconcave-curved light-emitting portion 7222. This is suitable forilluminating a specific range because light emitted from thelight-emitting portion 7222 is collected to the front of the lightingdevice 7220.

The light-emitting portion included in each of the lighting devices7200, 7210, and 7220 is flexible; thus, the light-emitting portion maybe fixed on a plastic member, a movable frame, or the like so that anemission surface of the light-emitting portion can be bent freelydepending on the intended use.

Note that although the lighting device in which the light-emittingportion is supported by the stage is described as an example here, ahousing provided with a light-emitting portion can be fixed on a ceilingor suspended from a ceiling. Since the light-emitting surface can becurved, the light-emitting surface is curved to have a concave shape,whereby a particular area can be brightly illuminated, or thelight-emitting surface is curved to have a convex shape, whereby a wholeroom can be brightly illuminated.

Here, each light-emitting portion includes the light-emitting device ofone embodiment of the present invention. In accordance with oneembodiment of the present invention, a highly reliable lighting devicehaving a curved light-emitting portion can be provided at a high yield.

FIG. 12F illustrates an example of a portable display device. A displaydevice 7300 includes a housing 7301, a display portion 7302, operationbuttons 7303, a display portion pull 7304, and a control portion 7305.

The display device 7300 includes a rolled flexible display portion 7302in the cylindrical housing 7301.

The display device 7300 can receive a video signal with the controlportion 7305 and can display the received video on the display portion7302. In addition, a battery is included in the control portion 7305.Moreover, a terminal portion for connecting a connector may be includedin the control portion 7305 so that a video signal or power can bedirectly supplied from the outside with a wiring.

With the operation buttons 7303, power ON/OFF, switching of displayedvideos, and the like can be performed.

FIG. 12G illustrates the display device 7300 in a state in which thedisplay portion 7302 is pulled out with the display portion pull 7304.Videos can be displayed on the display portion 7302 in this state.Further, the operation buttons 7303 on the surface of the housing 7301allow one-handed operation. The operation button 7303 is provided not inthe center of the housing 7301 but on one side of the housing 7301 asillustrated in FIG. 12F, which makes one-handed operation easy.

Note that a reinforcement frame may be provided for a side portion ofthe display portion 7302 so that the display portion 7302 has a flatdisplay surface when pulled out.

Note that in addition to this structure, a speaker may be provided forthe housing so that sound is output with an audio signal receivedtogether with a video signal.

The display portion 7302 includes the light-emitting device of oneembodiment of the present invention. In accordance with one embodimentof the present invention, a lightweight and highly reliablelight-emitting device can be provided at a high yield.

This embodiment can be combined with any of the other embodiments asappropriate.

This application is based on Japanese Patent Application serial no.2013-160042 filed with Japan Patent Office on Aug. 1, 2013, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A light-emitting device comprising: a firstflexible substrate; a second flexible substrate; an element layerbetween the first flexible substrate and the second flexible substrate;a first bonding layer between the first flexible substrate and theelement layer; and a second bonding layer between the second flexiblesubstrate and the element layer, wherein the element layer comprises alight-emitting element, wherein the first bonding layer and the secondbonding layer extend beyond an end portion of the element layer and arein contact with each other, and wherein the first flexible substrate andthe second flexible substrate extend beyond the end portion of theelement layer, an end portion of the first bonding layer, and an endportion of the second bonding layer and are in contact with each other.2. The light-emitting device according to claim 1, wherein the secondbonding layer is in contact with a side surface of the end portion ofthe element layer.
 3. The light-emitting device according to claim 1,wherein the second flexible substrate is in contact with side surfacesof the end portions of the first bonding layer and the second bondinglayer.
 4. The light-emitting device according to claim 1, wherein anabsolute value of a difference between a thermal expansion coefficientof the first flexible substrate and a thermal expansion coefficient ofthe second flexible substrate is smaller than or equal to 10% of thethermal expansion coefficient of the first flexible substrate or thethermal expansion coefficient of the second flexible substrate.
 5. Thelight-emitting device according to claim 1, wherein the first flexiblesubstrate and the second flexible substrate comprise a same material. 6.A light-emitting device comprising: a first flexible substrate; a secondflexible substrate; an element layer between the first flexiblesubstrate and the second flexible substrate; a first bonding layerbetween the first flexible substrate and the element layer, a secondbonding layer between the second flexible substrate and the elementlayer, and a third bonding layer between the first flexible substrateand the second flexible substrate, wherein the element layer comprises alight-emitting element, wherein the first flexible substrate and thesecond flexible substrate extend beyond an end portion of the elementlayer, an end portion of the first bonding layer, and an end portion ofthe second bonding layer, and wherein the first flexible substrate andthe second flexible substrate overlap with each other with the thirdbonding layer therebetween in a region not overlapping with the elementlayer, the first bonding layer, and the second bonding layer.
 7. Thelight-emitting device according to claim 6, wherein the third bondinglayer does not overlap with the element layer, the first bonding layer,and the second bonding layer.
 8. The light-emitting device according toclaim 6, wherein the third bonding layer is in contact with a sidesurface of the end portion of the first bonding layer.
 9. Thelight-emitting device according to claim 6, wherein the second flexiblesubstrate is in contact with side surfaces of the end portions of theelement layer, the first bonding layer, and the second bonding layer.10. The light-emitting device according to claim 6, wherein the thirdbonding layer comprises a low-melting-point glass or a thermoplasticresin.
 11. The light-emitting device according to claim 6, wherein anabsolute value of a difference between a thermal expansion coefficientof the first flexible substrate and a thermal expansion coefficient ofthe second flexible substrate is smaller than or equal to 10% of thethermal expansion coefficient of the first flexible substrate or thethermal expansion coefficient of the second flexible substrate.
 12. Thelight-emitting device according to claim 6, wherein the first flexiblesubstrate and the second flexible substrate comprise a same material.13. A light-emitting device comprising: a first flexible substrate; asecond flexible substrate; an element layer between the first flexiblesubstrate and the second flexible substrate; a first bonding layerbetween the first flexible substrate and the element layer; and a secondbonding layer between the second flexible substrate and the elementlayer, wherein the element layer comprises a light-emitting element,wherein the first flexible substrate, the second flexible substrate, andthe second bonding layer extend beyond an end portion of the elementlayer and an end portion of the first bonding layer, and wherein thefirst flexible substrate and the second flexible substrate overlap witheach other with the second bonding layer therebetween in a region notoverlapping with the element layer and the first bonding layer.
 14. Thelight-emitting device according to claim 13, wherein the first flexiblesubstrate and the second flexible substrate extend beyond the endportion of the element layer, the end portion of the first bondinglayer, and an end portion of the second bonding layer and are in contactwith each other.
 15. The light-emitting device according to claim 13,wherein the second bonding layer is in contact with side surfaces of theend portions of the element layer and the first bonding layer.
 16. Thelight-emitting device according to claim 14, wherein the second flexiblesubstrate is in contact with a side surface of the end portion of thesecond bonding layer.
 17. The light-emitting device according to claim13, wherein an absolute value of a difference between a thermalexpansion coefficient of the first flexible substrate and a thermalexpansion coefficient of the second flexible substrate is smaller thanor equal to 10% of the thermal expansion coefficient of the firstflexible substrate or the thermal expansion coefficient of the secondflexible substrate.
 18. The light-emitting device according to claim 13,wherein the first flexible substrate and the second flexible substratecomprise a same material.